Then he had found out what was going on in Athens where his father ruled (monarchy). The master of Crete was making 14 kids from Athens go to the maze and fight the minotaur (A monster that is half- Bull -half Man).
This is the maze the Minotaur was in.
Theseus told his dad he was going to kill the bull/man so they would not have to do this any more and when he returned to Athens he would have white sails.
He went to Crete and meet King Minos daughter which had fallen in love with him and gave him a ball of string so he could find his way back out of the maze as long as he took her home with him.
Next he went in to the maze and defended the bull/man and then followed the string back out.
Then they set off with the king's daughter but when they stopped on an island he forgot her.
When he returned he forgot to turn the sails to white so his dad killed himself by jumping off the cliff.